Motor controller

ABSTRACT

A motor is equipped with a magnetic-flux detector, which detects magnetic fluxes from magnets of the motor. A position signal converter finds a position of the motor using a value detected by magnetic-flux detector. A speed controller throws the motor in sine wave drive using the detected motor position.

This Application is a U.S. National Phase Application of PCTInternational Application PCT/JP02/10645 Oct. 15, 2002.

TECHNICAL FIELD

The present invention relates to a motor controller that drives asynchronous motor having magnets. The synchronous motor includes amagnetic flux detector for detecting a motor position. The motorcontroller of the present invention throws the synchronous motor in sinewave drive even at starting or transition.

BACKGROUND ART

A conventional motor controller is described hereinafter with referenceto FIG. 17 and FIG. 18. Driving a synchronous motor involves (a)detecting a position of magnetic pole of the motor, and (b) controllinga current or a voltage applied to windings of the motor responding to amagnetic pole signal (CS signal) indicating the position of magneticpole of the motor.

FIG. 17 shows rectangular wave drive of a three-phase motor. Based on alogic of magnetic-pole signals CS1, CS2, and CS3 of the three-phase, arectangular wave drive of 120 degrees is applied to phases U, V and W ofthe motor. Power is usually supplied during this 120 degrees period.FIG. 18 shows a sine wave drive of the three-phase motor. A sine wavedrive applied to the phases U, V and W of the motor using (a) a changepoint of the CS signals' logic and (b) a positional information from thechange point produced by a position detector of high resolution, such asan encoder, separately mounted. In this sine-wave drive, power issupplied during 180 degrees period.

The sine wave drive is desirable because it can drive a motorefficiently with less vibrations. However, as described above, CSsignals simply throw a motor in rectangular wave drive, thus a motorcontroller needs a positional detector such as an encoder for obtainingpositional information in order to throw the motor in sine wave drive.The positional detector should be mounted separately, which isunfavorable to the motor controller in view of the cost and size. Even amotor controller including an encoder is obliged to drive the motor witha rectangular wave at initial starting because an absolute positioncannot be detected during a period from the starting to a first changeof a CS signal. In this period, the motor cannot be driven with a sinewave, and the rectangular wave drive is only a choice.

Japanese Patent Application Non-examined Publication No. H10-201284discloses that a constant speed drive of a motor allows sine wave driveby dividing intervals between change points of the logic of the CSsignal. The intervals are measured by a timer, and the intervals aredivided by the measured values. However, this method cannot deal with agreat change in a motor speed or a transient period, so that the sinewave cannot be kept going.

SUMMARY OF THE INVENTION

The present invention addresses the problem discussed above, and aims toprovide a motor controller that comprises the following elements:

-   -   (a) a motor;    -   (b) magnetic flux detecting means for detecting a magnetic flux        of the motor directly or indirectly;    -   (c) a position detecting means for converting an amount of the        detected magnetic flux to a position of the motor; and    -   (d) control means for driving the motor with a sine wave using a        detected position by the position detecting means.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a structure of a motor controller in accordance with afirst exemplary embodiment of the present invention.

FIG. 2 shows an example of magnetic pole signals.

FIG. 3 shows an example of magnetic pole signals and motor driving waveforms.

FIG. 4 shows another example of magnetic pole signals.

FIG. 5 shows a structure of a motor controller in accordance with asecond exemplary embodiment of the present invention.

FIG. 6 shows an example of magnetic pole signals.

FIG. 7 shows another example of magnetic pole signals.

FIG. 8 shows a structure of a motor controller in accordance with athird exemplary embodiment of the present invention.

FIG. 9 shows an example of magnetic pole signals.

FIG. 10 shows an example of magnetic pole signals corrected by amagnetic-flux mapping device.

FIG. 11 shows an example of an error of positional information suppliedfrom a position signal converter.

FIG. 12 shows a structure of a motor controller in accordance with afourth exemplary embodiment of the present invention.

FIG. 13 shows a structure of a motor controller in accordance with afifth exemplary embodiment of the present invention.

FIG. 14 shows an example of magnetic pole signals corrected by amagnetic-flux mapping device.

FIG. 15 shows an example of an error of positional information suppliedfrom a position signal converter.

FIG. 16 shows a structure of a motor controller in accordance with asixth exemplary embodiment of the present invention.

FIG. 17 shows a waveform of a magnetic pole position sensor and arectangular wave drive of prior art.

FIG. 18 shows a waveform of a magnetic pole position sensor and a sinewave drive of prior art.

PREFERRED EMBODIMENT OF THE PRESENT INVENTION

Exemplary embodiments of the present invention are demonstratedhereinafter with reference to the accompanying drawings.

Exemplary Embodiment 1

FIG. 1 shows a structure of a motor controller in accordance with thefirst exemplary embodiment of the present invention. Three-phasesynchronous motor 100 is equipped with magnetic-flux detector 102, whichdetects magnetic flux of motor's magnets and outputs three-phasesinusoidal wave magnetic-pole signals CS1, CS2 and CS3 having phasedifferences of approx. 120 degrees in between respectively.Magnetic-flux detector 102 is fixed to a stator winding of the motorsuch that the magnetic-pole signals become in phase with a line-to-lineinduction voltage of motor 100.

Magnetic-pole signals CS1, CS2 and CS3 are fed into position signalconverter 110 in order to find a position of the motor. Converter 110converts analog values of the magnetic-pole signals into digital values,and performs inverse trigonometric function computation, thereby findinga position of the motor. The inverse trigonometric function computationcan be performed using any one of the magnetic-pole signals CS1, CS2 andCS3; however, as shown in FIG. 2, a use of an area less than a half ofthe amplitude, where respective signals cross each other, results in amore accurate computation. To be more specific, perform a computation byswitching the magnetic-pole signals at a threshold value half of anamplitude, then converting into a position of one cycle of themagnetic-pole signal using a sign of the magnetic-pole signal. Thismethod advantageously reduces an amount of tables used in the inversetrigonometric function computation.

Positional information from position signal converter 110 allows toprovide the three phases (phases U, V and W) with sine wave drive asshown in FIG. 3. The magnetic-pole signals, as already discussed, are inphase with line-to-line induction voltages. Thus the phases of phases U,V and W are shifted from those of the magnetic-pole signals by 30degrees as illustrated so that the current waveforms of phases U, V andW can be in proper phaseal relation with those of the induction voltagesof the respective phases. In the case of a voltage drive, a phase of thevoltage is advanced responsive to a speed or a load of the motor so thatthe phases of the currents can be in proper phaseal relation with thevoltage.

Differentiator 108 converts positional information into a motor speed.Speed controller 106 outputs an instruction to PWM pulse widthmodulation) controller 104 so that the motor speed can follow aninstructed speed. Not only the speed control described here, but alsoposition control or torque control is available. PWM controller 104throws motor 100 in PWM drive following the control instruction. It isnot necessarily the PWM drive, but linear drive by a power operationamplifier can be available.

The foregoing structure allows the magnetic-flux detector to detect ananalog amount of magnetic flux, so that the magnetic-pole position canbe monitored from a turn-on which starts driving the motor. As a result,a motor can be driven with a sine wave from an initial turn-on. When aspeed of the motor changes a lot, e.g., a transient response period, themotor can be kept driving with the sine waveform without adding aposition detector such as an encoder.

In this embodiment, a three-phase synchronous rotary motor isdemonstrated, however, other motors including a two-phase motor, astepping motor, or a liner motor can be driven with a sine wave. As thisembodiment proves, a number of phases of the motor does not always agreewith a number of the magnetic flux detectors. For instance, as shown inFIG. 4, a two-phase magnetic flux detector can be used. This detectoroutputs sine waves having a phase difference of 90 degrees. In the caseof two-phase, the inverse trigonometric function computation can beperformed with one of signals CS1 or CS2; however a use of an area, aproduct of the square root of 0.5 multiplied by an amplitude whererespective magnetic-pole signals cross each other, results in a moreaccurate computation. In other words, a product of multiplying anamplitude by the square root of 0.5 is used as a threshold value atwhich the magnetic-pole signals are switched for calculation.

The magnetic flux detector does not always directly detect a magneticflux of a motor, but it can detect a magnetic flux indirectly. In otherwords, a magnetic-flux detector including a sensor magnet and an MRsensor can be used. This detector outputs a sine wave having the samecycle as the motor's magnetic flux.

Exemplary Embodiment 2

A motor controller in accordance with the second embodiment can correctinfluence of a tertiary harmonic component applied to three-phasemagnetic-pole signals CS1, CS2 and CS3, or influence by off-sets in therespective signals.

FIG. 5 shows a structure of the motor controller in accordance with thesecond embodiment of the present invention. Motor 100 is equipped withmagnetic-flux detector 102, which detects magnetic flux of motor'smagnets and outputs three-phase sinusoidal wave magnetic-pole signalsCS1, CS2 and CS3 having phase differences of approx. 120 degrees inbetween respectively. However, actual waveforms of the magnetic-polesignals often include offsets similar to each other in three phasesrespectively as shown in FIG. 6, or actual waveforms of the signals areoften distorted as shown in FIG. 7 because of tertiary harmoniccomponents included in the signals. The magnetic-pole signals arecorrected by neutral-point corrector 200 in the following way:

Ideal forms of magnetic-pole signals CS1, CS2 and CS3 are expressedCS1r, CS2r and CS3r using angle θ and amplitude “A” of each one of thesignals as follows:CS 1 r=A·sin(θ)  (formula 1)CS 2 r=A·sin(θ−2π/3)  (formula 2)CS 3 r=A·sin(θ+2π/3)  (formula 3)The total sum of the three signals is 0 (zero).CS 1 r+CSr 2+CSr 3=0  (formula 4)

On the other hand, actual magnetic-pole signals CS1, CS2 and CS3including offsets or amplitude “B” of tertiary harmonic components areexpressed in the following equations.CS 1=A·sin(θ)+B·sin(3·θ)+offset  (formula 5)CS 2=A·sin(θ−2π/3)+B·sin{3·(θ−2π/3)}+offset  (formula 6)CS 3=A·sin(θ+2 π/3)+B·sin{3·(θ+2π/3)}+offset  (formula 7)The signals average out: CSave=(CS 1 +CS 2+CS 3)/3=B·sin(3·θ)+offset  (formula 8)

The subtraction of this CSave from the actual magnetic-pole signals cancorrect the actual signals to be ideal forms CS1r, CS2r and CS3r wherethe offsets or the tertiary harmonic components are removed. Neutralpoint corrector 200 outputs the ideal forms of magnetic-pole signalsthus corrected. The corrected magnetic-pole signals can be also founddirectly from the following equations instead of using the CSave:CS 1 r=(2·CS 1−CS 2−CS 3)/3  (formula 9)CS 2 r=(2·CS 2−CS 3−CS 1)/3  (formula 10)CS 3 r=(2·CS 3−CS 1−CS 2)/3  (formula 11)

Position signal converter 110 finds a position of the motor throughinverse trigonometric function computation in the same manner as thefirst embodiment based on the corrected magnetic-pole signals suppliedfrom neutral-point corrector 200, then outputs positional information.Based on this positional information, sine-wave drive and speed controlare provided to the motor using differentiator 108, speed controller 106and PWM controller 104.

The foregoing structure allows the motor controller to correctthree-phase magnetic-pole signals detected by the magnetic-flux detectorwith ease even the signals include offsets or tertiary harmoniccomponents which distort the waveforms of the signals. As a result, themotor can be driven with a sine wave from an initial turn-on. When aspeed of the motor changes a lot, e.g., a transient response period, themotor can be kept driving with the sine wave without adding a positiondetector such as an encoder at an inexpensive cost and with ease. Thisembodiment proves that the signals including both of the offsets and theharmonic components can be corrected with ease.

Exemplary Embodiment 3

A motor controller in accordance with the third embodiment can suppressinfluence of the shift of magnetic-pole signals from an ideal sine wave,e.g., one of the signals includes an offset or a high-order harmoniccomponent, or each one of phase differences between three-phasemagnetic-pole signals is shifted from 120 degrees. The motor controllerthus can assure monotonic increase of the detected positional values.

FIG. 8 shows a structure of the motor controller in accordance with thethird embodiment of the present invention. Motor 100 is equipped withmagnetic-flux detector 102, which detects magnetic flux of motor'smagnets and outputs three-phase sinusoidal wave magnetic-pole signalsCS1, CS2 and CS3 having phase differences of approx. 120 degrees inbetween respectively. Actual waveforms of the signals include offsets orharmonic components, or respective amplitudes differ from each other asshown in FIG. 9. Magnetic-flux mapping device 300 correct influence bythe distortion of the magnetic-pole signals in the following way:

The sum (CSgain) of the respective squares of ideal signals CS1r, CS2rand CS3r equals to the product of multiplying the square of amplitude Aby 1.5 as expressed in the following equation:CSgain=CS 1 r ² +CS 2 r ² +CS 3 r ²=1.5×A ²  (formula 12)

On the other hand, actual magnetic-pole signals CS1, CS2 and CS3 areexpressed in the following equations due to changes in amplitude A,offsets, harmonic components and phase θ.CS 1=A 1 ·sin(θ+θ1)+offset 1  (formula 13)CS 2=A 2 ·sin(θ+θ2−2π/3)+offset 2  (formula 14)CS 3=A 3 ·sin(θ+θ3+2π/3)+offset 3  (formula 15)

Each one of three magnetic-pole signals is divided by a square root ofCSgain (sum of squares of respective three magnetic-pole signals),thereby correcting the three signals to have a constant amplitude intheir three phases as shown in FIG. 10. In other words, magnetic fluxmapping device 300 calculates sum of squares of respective threemagnetic-pole signals, and divides each one of three magnetic-polesignals by the square root thereof. As a result, device 300 maps the sumof squares of respective three magnetic-pole signals to be constant, andcorrects influence by the distortion of the original signals. Anamplitude after the correction is not necessary to fit that of theoriginal signal, and can be set at any value.

Based on the corrected signals supplied from mapping device 300,position signal converter 110 finds a position of the motor throughinverse trigonometric function computation and outputs positionalinformation. The inverse trigonometric function computation can beperformed with one of signals CS1, CS2 and CS3, however, a use of anarea under half of an amplitude, where corrected magnetic-pole signalscross each other, results in a more accurate computation. To be morespecific, a computation by switching the magnetic-pole signals at athreshold value half of an amplitude, and converting into a position ofone cycle of the magnetic-pole signal using a sign of the magnetic-polesignal is performed.

In the case of using of an area under half of an amplitude wherecorrected magnetic-pole signals cross each other, neutral-pointcorrector 200, which is described in the second embodiment, can bedisposed between magnetic-flux detector 102 and magnetic flux mappingdevice 300. Even a computation by switching the magnetic-pole signals ata threshold value half of an amplitude is performed, the motorcontroller can assure monotonic increase by correcting influence of thedistortion of the signals. This method advantageously reduces an amountof tables used in the inverse trigonometric function computation.

This is a similar operation to the first embodiment. FIG. 10 shows thesignals mapped by mapping device 300, and FIG. 11 shows the positionalinformation converted from the signals shown in FIG. 10. As such, evenif an original signal includes distortion, influence due to thedistortion can be suppressed, so that positional information with asmaller error is obtainable. Based on this positional information,sine-wave drive and speed control are provided to the motor usingdifferentiator 108, speed controller 106 and PWM controller 104.

The foregoing structure allows the motor controller to correctthree-phase magnetic-pole signals detected by the magnetic-flux detectorwith ease. The motor controller thus can assure monotonic increase ofthe detected positional values. As a result, the motor can be drivenwith a sine wave from an initial turn-on. When a speed of the motorchanges a lot, e.g., a transient response period, the motor can be keptdriving with the sine wave without adding a position detector such as anencoder at an inexpensive cost and with ease. In this third embodiment,the magnetic-pole signal is divided by the square root of the sum ofsquares of the three-phase magnetic-pole signals, thereby finding aplace of the motor; however, the square of a magnetic-pole signal can bedivided by the sum of the squares of the three-phase magnetic-polesignals, so that the motor position is found.

Exemplary Embodiment 4

A motor controller in accordance with the fourth embodiment detectsmagnetic-pole signals of only any two phases out of three-phasemagnetic-pole signals for throwing the motor in sine wave drive.

FIG. 12 shows a structure of the motor controller in accordance with thefourth embodiment of the present invention. Motor 100 is equipped withmagnetic-flux detector 102, which detects magnetic flux of motor'smagnets and outputs any two signals out of three-phase magnetic-polesignals CS1, CS2 and CS3. Sinusoidal wave magnetic-pole signals CS1, CS2and CS3 having phase differences of approx. 120 degrees in betweenrespectively; however, they are converted by the followingthree-phase/two-phase conversion into two-phase signals CSa and CSbhaving a phase difference of 90 degrees in sinusoidal waves.$\begin{matrix}{\begin{pmatrix}{CSa} \\{CSb}\end{pmatrix} = {K\quad\begin{pmatrix}1 & {- \frac{1}{2}} & {- \frac{1}{2}} \\0 & \frac{\sqrt{3}}{2} & {- \frac{\sqrt{3}}{2}}\end{pmatrix}\quad\begin{pmatrix}{CS1} \\{CS2} \\{CS3}\end{pmatrix}}} & \left( {{formula}\quad 16} \right)\end{matrix}$where K=an any constant.As already discussed in the second embodiment, the total sum of signalsCS1, CS2 and CS3 is 0 (zero). Thus detection of any two signals in theabove equation allows the three-phase/two-phase conversion. Two-phaseconverter 400 takes any two signals in analog values out of three-phasemagnetic-phase signals into an A/D converter, and converts them totwo-phase magnetic-pole sinusoidal wave signals CSa and CSb having aphase difference of 90 degrees.

If the signals CS1, CS2 and CS3 shift largely from ideal sine waves, theforegoing equation can be modified to the following equation, so thatthe sum and the difference of two magnetic-pole signals can be used.This method can disperse the influence of the shift. $\begin{matrix}{\begin{pmatrix}{CSa} \\{CSb}\end{pmatrix} = {K\quad\begin{pmatrix}{- \frac{3}{2}} & {- \frac{3}{2}} \\\frac{\sqrt{3}}{2} & {- \frac{\sqrt{3}}{2}}\end{pmatrix}\quad\begin{pmatrix}{CS2} \\{CS3}\end{pmatrix}}} & \left( {{formula}\quad 17} \right)\end{matrix}$

Based on signals CSa and CSb converted by converter 400, position signalconverter 402 finds a position of the motor through inversetrigonometric function computation, and outputs positional information.The inverse trigonometric function computation is used in either one ofsignal CSa or signal CSb. However, it can be used in an area less thanthe product of multiplying the amplitude, where the respective signalscross each other, by the square root of 0.5. This method results in amore accurate computation. To be more specific, a product of multiplyingan amplitude by the square root of 0.5 is used as a threshold value atwhich the converted magnetic-pole signals are switched for calculation,and signs of the converted signals CSa and CSb are used for conversioninto a position of one cycle of the magnetic-pole signals. This methodreduces an amount of tables used in the computations. Based on thepositional information supplied from position signal converter 402,sine-wave drive and speed control are provided to the motor usingdifferentiator 108, speed controller 106 and PWM controller 104. This issimilar to the first exemplary embodiment.

The foregoing structure allows the motor controller to detect a positionof the motor with any two magnetic-pole signals detected out ofthree-phase magnetic-pole signals. As a result, the motor can be drivenwith a sine wave from an initial turn-on. When a speed of the motorchanges a lot, e.g., a transient response period, the motor can be keptdriving with the sine wave without adding a position detector such as anencoder at an inexpensive cost and with ease.

Exemplary Embodiment 5

A motor controller in accordance with the fifth embodiment of thepresent invention allows to throw the motor in sine wave drive bydetecting any two-phase magnetic-pole signals out of three-phasemagnetic-pole signals. This is similar to the fourth embodiment.Further, the fifth embodiment assures monotonic increase of the detectedpositional values by suppressing the influence due to the shift of thethree-phase signals from ideal sine waves.

FIG. 13 shows a structure of the motor controller in accordance with thefifth embodiment of the present invention. Motor 100 is equipped withmagnetic-flux detector 102, which detects magnetic flux of motor'smagnets and outputs three-phase sinusoidal wave magnetic-pole signalsCS1, CS2 and CS3 having phase differences of approx. 120 degrees inbetween respectively. Actual waveforms of the signals include offsets orharmonic components as same as the third embodiment, and are thusdistorted as shown in FIG. 9.

Two-phase converter 400 converts any two signals out of the three-phasemagnetic-pole signals CS1, CS2 and CS3 into two-phase sinusoidal wavesignals CSa and CSb having a phase difference of 90 degrees. This issimilar to the fourth embodiment. The distortions of the three-phasesignals cause distortions in the waveforms of signals CSa and CSb.Magnetic-flux mapping device 500 corrects the influence of thedistortions in the following way:

Ideal forms of two-phase signal are expressed in the following equationsusing angle θ and amplitude A of a magnetic-pole signal:CSar=A·cos(θ)  (formula 18) CSbr=A·sin(θ)  (formula 19)The sum of squares of these two signals is the square of amplitude “A”as showed in the equation below:CSgain=CSar ² +CSbr ² =A ²  (formula 20)

On the other hand, in the actual signals CSa and CSb, respectiveamplitudes change and the shift due to offsets or harmonic componentsare added in addition to phase shift. Respective magnetic-pole signalsare divided by the square root of CSgain (sum of the squares of the twosignals CSar and CSbr), so that signals CSa and CSb are corrected tohave a constant amplitude as shown in FIG. 14. In other words, mappingdevice 500 finds the sum of squares of two-phase magnetic-pole signals,and divides the respective signals by the square root of this sum,thereby mapping the two-phase signals such that the sum of the squaresof the two-phase signals stays constant. As a result, the distortions ofthe original signals are corrected. Amplitudes after the correction canbe set at any value.

Based on signals CSa and CSb corrected by mapping device 500, positionsignal converter 402 finds a position of the motor through inversetrigonometric function computation, and outputs positional information.This is similar to the fourth embodiment. This computation is performed,as shown in FIG. 14, by switching the magnetic-pole signals at athreshold value that is a product of multiplying an amplitude by thesquare root of 0.5. The correction of the distortion by mapping device500 assures monotonic increase of the detected positional values even atswitching. The signals mapped by mapping device 500 in FIG. 14 areconverted into positional information as shown in FIG. 15. As such, evenif an original signal includes distortion, influence due to thedistortion can be suppressed, so that positional information with asmaller error is obtainable. Based on the positional informationsupplied from position signal converter 402, sine-wave drive and speedcontrol are provided to the motor using differentiator 108, speedcontroller 106 and PWM controller 104. This is similar to the firstexemplary embodiment.

The foregoing structure allows the motor controller to suppress theinfluence of the shift when the controller detects any two magnetic-polesignals out of three-phase magnetic-pole signals shifted from ideal sinewaves. Thus the controller can assure monotonic increase of the detectedpositional values. As a result, the motor can be driven with a sine wavefrom an initial turn-on. When a speed of the motor changes a lot, e.g.,a transient response period, the motor can be kept driving with the sinewave without adding a position detector such as an encoder at aninexpensive cost and with ease. In this fifth embodiment, themagnetic-pole signal is divided by the square root of the sum of squaresof the two-phase magnetic-pole signals; however, the square of themagnetic-pole signal can be divided by the sum of squares of thetwo-phase magnetic-pole signals.

Exemplary Embodiment 6

The embodiments discussed previously allow to detect a position of themotor within a cycle from a magnetic-pole signal to anothermagnetic-pole signal. However, a high speed spin of a motor sometimesdoes not provide a time span short enough to detect a magnetic-polesignal. In such a case, a position detection shifts by an integralmultiple of a cycle of the magnetic-pole signal. A motor controller inaccordance with the sixth embodiment allows a position detection even ata long time span for detecting a magnetic-pole signal.

FIG. 16 shows a structure of the motor controller in accordance with thesixth embodiment of the present invention. Motor 100 is equipped withmagnetic-flux detector 102, which detects magnetic flux of motor'smagnets and outputs three-phase sinusoidal wave magnetic-pole signalsCS1, CS2 and CS3 having phase differences of approx. 120 degrees inbetween respectively.

Comparator 600 converts any two signals out of three-phase magnetic-polesignals CS1, CS2 and CS3 into rectangular waves. Counter 602, an up-downcounter, receives the two rectangular waves, which comparator 600outputs, and outputs values of four times multiplication of the cyclesof magnetic-pole signals, namely, outputs four counts per a cycle.Position signal converter 604 finds a position signal of the motor usingboth of the motor position found through inverse trigonometric functioncomputation provided to magnetic-pole signals CS1, CS2 and CS3 detectedby a magnetic-flux detector 102 and the values counted by counter 602.Whenever the number of output-counters of counter 602 increases four,position signal converter 604 recognizes increase of one cycle, andoutputs positional information. This method allows to detect a positionsignal free from the shift of position detection by an integral multipleof the cycle of the magnetic-pole signal, even if the motor spins at ahigh speed and a signal detection cycle by converter 604 is longer thana half cycle of the magnetic-pole signal.

Positional information from position signal converter 604 is convertedto a motor speed by differentiator 108, and speed controller 106 outputsan instruction to PWM (pulse width modulation) controller 104 so thatthe motor speed can follow an instructed speed. Not only the speedcontrol described here, but also position control or torque control isavailable.

The foregoing structure allows the motor controller to detect the motorposition even when the motor spins at a high speed, which does notprovide a time span small enough to detect the magnetic-pole signal.

Industrial Applicability

The motor controller of the present invention throws a synchronous motoralways in sine wave drive even at starting or transition, thus thecontroller is suitable for driving calmly a synchronous motor with lessvibrations.

Reference numerals in the drawings 100 Motor 102 Magnetic-flux detector104 PWM controller 106 Speed controller 108 Differentiator 110, 402, 604Position signal converter 200 Neutral point corrector 300, 500Magnetic-flux mapping device 400 Two-phase converter 600 Comparator 602Counter

1. A motor controller for driving a motor having a rotor, which includesmagnet, said motor controller comprising: a) a magnetic flux detectorfor detecting a magnetic flux from said magnets and obtaining a magnetpole signal; b) a position signal converter for finding a position ofthe rotor based on the magnetic pole signal; c) a differentiator forfinding a speed signal based on the output of the position signalconverter; d) a speed controller for comparing the speed signal with apredetermined instructive speed, and outputting an instruction signal;and e) a PWM (pulse width modulation) controller for performing PWMdrive of the motor according to the instruction signal, wherein the PWMcontroller drives the motor in sine wave forms, and wherein the magneticpole signal is a two phase sine wave signal having a phase difference of90°.
 2. A motor controller for driving a motor having a rotor, whichincludes magnets, said motor controller comprising: a) a magnetic fluxdetector for detecting a magnetic flux from said magnets and obtaining amagnet pole signal; b) a position signal converter for finding aposition of the rotor based on the magnetic pole signal; c) adifferentiator for finding a speed signal based on the output of theposition signal converter; d) a speed controller for comprising thespeed signal with a predetermined instructive speed, and outputting aninstruction signal; and e) a PWM (pulse width modulation) controller forperforming PWM drive of the motor according to the instruction signal,wherein the PWM controller drives the motor in sine wave forms, andwherein the magnetic pole signal is a three phase sine wave signalhaving a phase difference of 120°, further comprising: a neutral pointcorrector for correcting the magnetic pole signal, wherein the magneticpole signal is corrected by the neutral point corrector and input intothe position signal converter.
 3. The motor controller according toclaim 2, wherein the neutral point corrector calculates an average valueof a sum of the magnetic pole signal and subtracts the average value ofthe sum from the magnetic pole signal of each phase.
 4. A motorcontroller for driving a motor having a rotor, which includes magnets,said motor controller comprising: a) a magnetic flux detector fordetecting a magnetic flux from said magnets and obtaining a magnet polesignal; b) a position signal converter for finding a position of therotor based on the magnetic pole signal; c) a differentiator for findinga speed signal based on the output of the position signal converter; d)a speed controller for comparing the speed signal with a predeterminedinstructive speed and outputting an instruction signal; and e) a PWM(pulse width modulation) controller for performing PWM drive of themotor according to the instruction signal, wherein the PWM controllerdrives the motor in sine wave forms, and wherein the magnetic polesignal is a three phase sine wave signal having a phase difference of120°, further comprising: a magnetic flux mapping device for correctingthe magnetic pole signal, wherein the magnetic pole signal is correctedby the magnetic flux mapping device and input into the position signalconverter.
 5. The motor controller according to claim 4, wherein themagnetic flux mapping device divides each one of the magnetic polesignals by a square root of a sum of squares of the magnetic polesignals.
 6. The motor controller according to claim 4, wherein themagnetic flux mapping device divides a square of each one of themagnetic pole signals by a sum of squares of the magnetic pole signals.7. A motor controller for driving a motor having a rotor, which includesmagnets, said motor controller comprising: a) a magnetic flux detectorfor detecting a magnetic flux from said magnets and obtaining a magnetpole signal; b) a position signal converter for finding a position ofthe rotor based on the magnetic pole signal; c) a differentiator forfinding a weed signal based on the output of the position signalconverter; d) a speed controller for comparing the speed signal with apredetermined instructive speed, and outputting an instruction signal;and e) a PWM (pulse width modulation) controller for performing PWMdrive of the motor according to the instruction signal wherein the PWMcontroller drives the motor in sine wave forms, and wherein the magneticpole signal is a three phase sine wave signal having a phase differenceof 120°, further comprising: a neutral point corrector for correctingthe magnetic pole signal and a magnetic flux mapping device forcorrecting a signal of the neutral point corrector in distortion,wherein the magnetic pole signal is corrected by the neutral pointcorrector and the magnetic flux mapping device, and input into theposition signal converter.
 8. The motor controller according to claim 7,wherein the position signal converter converts the magnetic pole signalby using a threshold not more than half of an amplitude of the magneticpole signal which has been corrected.
 9. A motor controller for drivinga motor having a rotor, which includes magnets said motor controllercomprising: a) a magnetic flux detector for detecting a magnetic fluxfrom said magnets and obtaining a magnet pole signal; b) a positionsignal converter for finding a position of the rotor based on themagnetic pole signal; c) a differentiator for finding a speed signalbased on the output of the position signal converter; d) a speedcontroller for comparing the speed signal with a predeterminedinstructive speed, and outputting an instruction signal; and e) a PWM(pulse width modulation) controller for performing PWM drive of themotor according to the instruction signal wherein the PWM controllerdrives the motor in sine wave forms, and wherein the magnetic polesignal is a three phase sine wave signal having a phase difference of120°, further comprising: a two-phase converter, wherein the two-phaseconverter converts the three phase sine wave signal having the phasedifference of 120° into a two phase sine wave signal having a phasedifference of 90°.
 10. The motor controller according to claim 9,wherein the two-phase converter converts into the two phase sine wavesignal having the phase difference of 90°, by using a sum and adifference of the magnetic pole signals of arbitrary two phases of thethree phase sine wave signal.
 11. The motor controller according toclaim 9, further comprising: a magnetic flux mapping device forcorrecting the magnetic pole signal, wherein the magnetic pole signal iscorrected in distortion by the magnetic flux mapping device and inputinto the position signal converter.
 12. The motor controller accordingto claim 11, wherein the magnetic flux mapping device divides each oneof the magnetic pole signals by a square root of a sum of squares of themagnetic pole signals.
 13. The motor controller according to claim 11,wherein the magnetic flux mapping device divides a square of each one ofthe magnetic pole signals by a sum of squares of the magnetic polesignals.
 14. The motor controller according to claim 11, wherein theposition signal converter converts the magnetic pole signal using athreshold which is obtained by multiplying a square root of 0.5 by anamplitude of the magnetic pole signal which has been corrected.
 15. Amotor controller for driving a motor having a rotor, which includesmagnets, said motor controller comprising: a) a magnetic flux detectorfor detecting a magnetic flux from said magnets and obtaining a magnetpole signal; b) a position signal converter for finding a position ofthe rotor based on the magnetic pole signal; c) a differentiator forfinding a speed signal based on the output of the position signalconverter; d) a speed controller for comparing the speed signal with apredetermined instructive speed, and outputting an instruction signal;and e) a PWM (pulse width modulation) controller for performing PWMdrive of the motor according to the instruction signal wherein the PWMcontroller drives the motor in sine wave forms, and wherein the magneticpole signal is a three phase sine wave signal having a phase differenceof 120°, further comprising; a comparator for converting the magneticpole signal into a rectangular wave; a counter for outputting a multiplenumber of a cycle of the magnetic pole signal based on an output of thecomparator, wherein the position signal converter finds positionalinformation using logical sum of the magnetic pole signal and an outputof the counter.
 16. The motor controller according to claim 15, whereinthe comparator inputs signals of arbitrary two phases of the magneticpole signal, and the counter outputs a quadruple value of a cycle of themagnetic pole signal.